Plurals of prepositions that become nouns

[LadyEdith]

Prepositions that become hyphenated nowns - for example:

Lie-down
Round-up
Drive-through

The plurals presumably are:

Lie-downs
Round-ups
Drive-throughs

I really don't like these constructions. They're ugly. It seems wrong to pluralise a preposition somehow.

What do you think?

at my own spelling mistake in Pedants' Corner! NOUNS!

They're kind of ugly, yes, but I can't think of a single time I've had to pluralise one of them!

Btw is "pluralise" an actual word even?

Well, life has its ups and downs, so hopefully someone will go into the ins and outs of nounifying prepositions.

Ah fair point Dad. But 'throughs'?

Funnily enough, I've just seen the word "breakthroughs" on the web and it sounds completely normal to me: "doctors have hailed a series of breakthroughs in the treatment of cancer..." So surely drivethroughs is also perfectly fine.

I think it's fine, actually. Shows the language is evolving to take on board new ways of expressing things.

The plural of compound nouns is a bit of a grey area as it depends on how the compound is formed in the first place. Add to this the hyphen in the OP's examples (normally the plural in hyphenated compounds falls on the first element (mothers-in-law) together with the fact that the examples given have phrasal verbs as their origin and it makes it even less clear.

The ones in the OP aren't in such common usage as "breakthroughs" in DDD's example, but in time, almost all hyphenated compounds lose their hyphen, as I imagine happened with "breakthrough" (also stemming from a phrasal verb)

So, what that means, but said a lot less succinctly, is, just add an S at the end.